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Magnetics question

2002 · Shift 0 · Q121

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2002 · Shift 0 · Q121

Magnetics question

2002 · Shift 0 · Q121

JEE MainPhysicsMagneticsMCQ+4 / −1

If a current is passed through a spring then the spring will

A
expand
B
compress
C
remains same
D
none of these

View written solutionFree

Correct answer: B

Physical idea
A spring is made of a conducting wire wound into many turns, like a helix. If current flows through it, then adjacent turns carry current in the same direction.
Interaction between adjacent turns
Each turn can be treated like a small circular loop. Two nearby parallel segments carrying current in the same direction attract each other due to magnetic force.
Effect on the spring
Since neighboring turns attract, the distance between successive turns decreases. Therefore the spring tends to shorten.
Conclusion
So, when current is passed through a spring, it will compress.
Option check

A: expand — Incorrect
B: compress — Correct
C: remains same — Incorrect
D: none of these — Incorrect

Therefore, the correct answer is $\boxed{\text{B}}$ .

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